Settable choke device to control the power setting of a variable displacement hyraulic pump

ABSTRACT

A power or moment regulation device for an adjustable hydraulic pump having a servo setting apparatus providing for a smooth stepless setting of the pump delivery quantity. In the device, the delivery quantity setting is determined in dependence upon the delivery pressure of the hydraulic pump in a delivery pressure line and a control pressure in a control line. The setting apparatus has a spring setting a pump setting member in the direction of maximum delivery quantity and a piston acting upon the pump setting member in the opposite direction of delivery quantity reduction. The piston is acted upon via a hydraulically actuated control valve with the delivery pressure. The actuation of the control valve is effected by the control pressure in the control line. A moment valve is provided, the closure force of which is determined by a metering spring arrangement connected with the pump setting member and biased in dependence upon the delivery quantity setting. The moment valve connects the control line with a discharge in dependence upon the control pressure in the control line and the biasing of the metering spring arrangement. A settable choke device, for setting the control pressure acting upon the control valve and the moment valve, is arranged in the control line branching off from the operating pressure line of the pump.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power or moment regulation device foran adjustable hydraulic pump having a hydraulic servo setting apparatusfor providing for a smooth stepless setting of the pump deliveryquantity. In the device, the delivery quantity setting is determined independence upon the delivery pressure of the hydraulic pump in adelivery pressure line and a control pressure in a control line. Thesetting apparatus has a spring setting the pump setting member in thedirection of maximum delivery quantity and at least one piston actingupon the pump setting member in the direction of delivery quantityreduction. The piston can be acted upon via a hydraulically actuatedcontrol valve with the delivery pressure or is connected with adischarge. The actuation of the control valve is effected by means ofthe control pressure in the control line, whereby a moment valve isprovided the closure force of which is determined by a metering springarrangement which is connected with the pump setting member and isbiased in dependence upon the delivery quantity setting. The momentvalve connects the control line with the discharge in dependence uponthe control pressure in the control line and the biasing of the meteringspring arrangement.

2. Description of the Prior Art

Such a regulation device is known from EP 0 149 787. This knownregulation device is operable either as a moment regulator or as powerregulator, in dependence upon whether or not a delivery flow choke,which may be adjustable, is provided in the delivery pressure line ofthe hydraulic pump. With such regulation devices there is a directfunctional relationship between the stroke volume of the pump and theload-dependent operating pressure upon which the control pressure actingupon the control valve is dependent. For moment regulation there appliesthe relationship that the product of operating pressure and strokevolume of the pump must be constant. If the speed of rotation of thepump is constant, moment regulation is at the same time powerregulation. With power regulators, changes in the speed of rotation ofthe pump, which affect for example the delivery flow quantity, areadditionally detected and regulated. A measure for the stroke volume ofthe hydraulic pump is the setting of the pump setting member which setsthe pump delivery quantity, which is connected via a metering springarrangement with the moment valve. The shape of the hyperbolic moment orpower characteristic is determined solely by the configuration of thecharacteristic of the metering spring arrangement.

This known power or moment regulation device is very strongly dependentupon the operating delivery quantity taken on the load side from theoperating pressure line. Upon an alteration of the operating deliveryquantity, the control oil quantity in the control line also changes, sothat the pump is displaced along its power hyperbola. A change of theposition of the power hyperbola, that is a change of the power settingof the pump, is possible only via the direct adjustment of the biasingof the metering spring arrangement by manual means. This adjustment byhand is very inconvenient and complex. In particular applications, forexample in excavator vehicles or the like, it is however necessary to beable to alter the power setting of the pump in dependence upon the kindof work being undertaken or in dependence upon the speed of rotation ofthe diesel motor driving the pump.

BRIEF SUMMARY OF THE INVENTION

Thus, an object of the present invention lies in the provision of apower or moment regulation device for an adjustable hydraulic pumphaving a hydraulic servo setting apparatus providing for smooth steplesssetting of the pump delivery quantity. In the device, the deliveryquantity setting is determined in dependence upon the delivery pressureof the hydraulic pump in a delivery pressure line and a control pressurein a control line. The setting apparatus has a spring urging a pumpsetting member in a first direction of maximum delivery quantity and atleast one piston urging the pump setting member in a second oppositedirection of delivery quantity reduction. The piston is acted upon via ahydraulically actuated control valve with the delivery pressure. Theactuation of the control valve is effected by the control pressure inthe control line. A moment valve is provided, the closure force of whichis determined by a metering spring arrangement which is connected withthe pump setting member and is biased in dependence upon the deliveryquantity setting. The arrangement is such that the moment valve connectsthe control line with the discharge in dependence upon the controlpressure in the control line and the biasing of the metering springarrangement. In this arrangement, the moment or power setting of thehydraulic pump can be altered by simple manner and means and can beadapted to changing working conditions or to different loads.

This object is achieved by means of a power or moment regulation devicein which the delivery pressure line branches into at least two operatingpressure lines, from each of which a respective control line branchesoff. In each of the control lines, a respective choke device isprovided, and the control lines are selectively connectable with thecontrol line by a selection valve. Each settable choke device can be anelectrical quantity-proportional valve, and can include a switch valveand choke arranged in parallel thereto. In greater detail, a choke canbe arranged in the control line between the settable choke device or theselection valve and the branch to the control valve and to the momentvalve. A delivery flow choke, which may be adjustable, is arranged inthe delivery pressure line, and the control pressure and the deliverypressure are taken off respectively downstream and upstream of thedelivery flow choke. Each settable choke device can be connected with acontrol device, by which different modes of operation of the hydraulicpump can be selected by a separate switch.

By means of the present invention it is thereby in particular possibleto alter the control pressure in the control line by means ofcorresponding setting of the settable choke device, even when theoperating delivery quantity taken on the load side out of the operatingpressure line is to remain constant. Thereby, the power setting of theadjustable hydraulic pump can be adapted quickly and in simple manner todiffering working conditions.

The settable choke device preferably consists of the electricallycontrolled quantity-proportional valve, through which the controlpressure in the control line can be steplessly or smoothly set. By meansof this configuration it is possible in an advantageous manner toseparately alter the power setting of the pump, for example throughactuation of a switch in the drivers cab of the excavator.

In the closed position of the control valve, the delivery flowregulation and the power regulation are switched off. In the workingposition of the quantity-proportional valve, delivery flow and powerregulation are adjustable in the same manner.

In a further configuration, the settable throttle device is formed of aswitch valve and a choke arranged parallel thereto. In this case, thepower and the delivery flow regulation are effective also with theswitch valve in closed position. In this exemplary embodiment there maybe arranged a further choke in the control line, between the settablechoke device, that is the switch valve and the choke parallel thereto,and the branch to the control valve and to the moment valve.

In a further configuration there is arranged in the delivery pressureline an adjustable delivery flow choke, between the hydraulic pump andthe branch of the control line. By means of this adjustable deliveryflow choke, variations in speed of rotation of the pump, which haveeffect on the delivery flow quantity, are, inter alia, detected by theregulator in accordance with the invention, which thus functions aspower regulator. If the adjustable delivery flow choke is not providedin the delivery pressure line, the regulator in accordance with theinvention represents a moment regulator.

Further, the settable choke device may be connected with a controldevice via which, by means of a separate switch, different modes ofoperation of the hydraulic pump can be set. By means of thisconfiguration it is possible to adapt the power setting of the pump tothe type of work been done in each case, by operation of the separateswitch arranged for example in the drivers cab of an excavator. Thereby,the control device can additionally be connected with a device formeasurement of the speed of rotation of the diesel, so that the powersetting of the pump can also be controlled or adjusted in dependenceupon the speed of rotation of the diesel.

BRIEF DESCRIPTION OF THE INVENTION

The present invention will be described in more detail below, withreference to preferred exemplary embodiments and with reference to theaccompanying drawings, which show:

FIG. 1 a first exemplary embodiment of a power or moment regulationdevice in accordance with the invention, in which the settable chokedevice is formed by a quantity-proportional valve,

FIG. 2 a second exemplary embodiment of the power or moment regulationdevice in accordance with the invention, in which the settable chokedevice is formed by a switch valve and a choke parallel thereto, and

FIG. 3 a schematic illustration of a further exemplary embodiment, inwhich the power setting of the pump can be altered by means of aseparate switch and a control device,

FIG. 4 a further exemplary embodiment of the present invention, in whichtwo operating pressure lines are provided with respective adjustablechoke devices, which have effect selectively on the power or momentregulation device in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a hydraulic pump 1 which is driven via a shaft 2 by meansof a drive source which is not illustrated. The hydraulic pump 1 may befor example an adjustable axial piston pump which has a pump settingmember 3 the tilt angle of which is proportional to the stroke volume ofthe hydraulic pump 1. A servo setting apparatus for the setting of thetilt angle of the hydraulic pump includes a spring 4 and a piston 5,acted upon by pressure, whereby the spring 4 adjusts the hydraulic pump1 to a maximum tilt angle, that is to maximum delivery volume. A piston6, which may be functionally integrated with the piston 5, assumes thereturn function in the direction of smaller tilt angles. The pistonsurface of the piston 6 is substantially larger than that of the piston5. The setting pressure of a setting pressure line 7, acting on thepiston 6, or on its piston surface, is taken off via a control valve 8and the line 9 from the delivery pressure line 10 of the hydraulicpump 1. A pressure limiting valve 11 is connected in series with thecontrol valve. The control valve is configured as a pressure balance andcan thus also be described as a pressure control valve and is acted uponon the one hand by the delivery pressure of the line 9 and on the otherhand by a control pressure of a control line 12. The control pressure orthe control oil quantity in the control line 12 is settable via asettable choke device 13 which is arranged in the control line 12. Thecontrol line 12 takes off the load-dependent operating pressure of thehydraulic pump 1 from an operating pressure line 15 behind a deliveryflow choke 16, which may be adjustable. The control oil quantity of thecontrol line can thus be altered, in a simple manner and way, by meansof the settable choke device 13. The delivery flow choke 16, which maybe settable, limits the delivery flow of the hydraulic pump 1 in thedelivery pressure line 10. In the configuration shown in FIG. 1, thedelivery pressure and the control pressure, which act upon the controlvalve 8, are taken off before and behind the delivery flow choke 16.Thus, in this case a power regulator is involved. If the delivery flowchoke 16 is not present, one has a moment regulator.

The moment valve 17 is on the one hand acted upon by the pressure of thecontrol line 12 and on the other hand by a metering spring arrangement18, the biasing of which is determined by the setting of the piston 6 orof the pump setting member 3. The moment valve 17 may connect thecontrol line 12 with a pressure-less discharge. If the control pressurein the control line 12 attains the value set at the moment valve 17,this discharge begins to open and there arises a pressure drop at thecontrol slide of the control valve 8. The control valve 8 is opened andthe piston 6 acted upon, via the setting pressure line 7, with a controlpressure and the piston, or the pump setting member 3, is displaced inthe direction of smaller delivery quantity. Thereby, at the same time,the metering spring arrangement 18 of the moment valve 17 is biased, sothat the pump is adjusted along the power hyperbola.

In the first exemplary embodiment shown in FIG. 1 the adjustable chokedevice 13 is formed by means of a quantity-proportional valve 13a, whichfor example may be electrically controlled. In the closed position ofthe quantity-proportional valve 13a, power and delivery flow regulationare switched off.

In the second exemplary embodiment shown in FIG. 2 the componentscorresponding to the first exemplary embodiment are provided with thesame reference signs. The construction and manner of functioning of thesecond exemplary embodiment correspond to the construction and manner offunctioning of the first exemplary embodiment. However, in the secondexemplary embodiment, the settable choke device 13 is formed by means ofa switch valve 13b and a choke 13c arranged parallel thereto. Ifappropriate, a further choke 14 may be provided between the choke device13 and the branch of the control line 12 to the control valve 8 and tothe moment valve 17. This further choke 14 limits the control oilquantity in the control line 12 when the switch valve 13b is located inthe opened position.

FIG. 3 shows a schematic overview of a further exemplary embodiment ofthe present invention. The settable choke device of the power or momentregulation device 22 of the pump 1 is connected with a control device 20which is controllable by means of a separate switch 21. By appropriatesetting of the switch 21 there can be set different modes of operation,that is power settings, of the pump. The illustrated switch 21 isdiscreetly adjustable, but a continuous mode of adjustment is alsopossible. Depending upon the type of work being done there can thus beprovided different power settings of the pump 1. It is particularlyfavourable that the switch 21 is separately arranged for example in thedrivers cab of an excavator. Further, there may be connected with thecontrol device 20, a device 23 for measurement of the speed of rotationof the diesel motor 25 driving the pump 1. By this means it is possibleto alter the power of the pump 1 in dependence upon the speed ofrotation of the diesel motor, continuously or discreetly.

FIG. 4 shows a further exemplary embodiment of the present invention, inwhich the components corresponding to those of the exemplary embodimentshown in FIG. 1 are provided with the same reference signs. Differentlyfrom the first exemplary embodiment, in the exemplary embodiment shownin FIG. 4 two operating pressure lines 15a, 15b are provided, whichbranch off from the delivery pressure line 10. With the two operatingpressure lines 15a, 15b different loads can be served, for example aloader block may be served by the operating pressure line 15a and anexcavator block by means of the operating pressure line 15b. The numberof operating pressure lines which branch off from the delivery pressureline 10 is, however, not limited to two as shown in the exemplaryembodiment illustrated in FIG. 4; the delivery pressure line 10 canbranch off into an arbitrary number of operating pressure line.

A control line 12a or 12b branches off from each operating pressure line15a, 15b, in which control lines respective settable choke devices 13aare provided. The illustrated settable choke devices are electricallycontrollable quantity-proportional valves 13a in accordance with theexemplary embodiment shown in FIG. 1, but in the exemplary embodimentshown in FIG. 4 the settable choke devices may also be of a switch valveand a choke arranged parallel thereto, as in the second exemplaryembodiment (FIG. 2). If more than two operating pressure lines areprovided, a control line branches off from each of these operatingpressure lines, in which control lines respective settable choke devicesare provided. As shown in FIG. 4, the two control lines 12a , 12b areselectively or alternatively connectable with the control line 12 via aselection valve 30. The functioning and effect of the control line 12has already been described in detail with reference to the firstexemplary embodiment shown in FIG. 1.

Also with the exemplary embodiment shown in FIG. 4, correspondingly tothe exemplary embodiments shown in FIGS. 1 and 2, a choke 14 may bearranged between the selection valve 30 and the branch of the controlline 12 to the control valve 8 and to the moment valve 17. This choke 14is, however, not shown in FIG. 4. Further, there can be arranged in thedelivery pressure line 10 a delivery flow choke 16--which may beadjustable--whereby the control pressure and the delivery pressure aretaken off respectively downstream of this choke 16 and upstream of thischoke 16, analogously to the embodiment illustrated in FIG. 1. This, ifappropriate adjustable, delivery flow chokes 16 is likewise not shown inFIG. 4. The settable choke devices 13a, 13a of the exemplary embodimentshown in FIG. 4 may, in accordance with the exemplary embodiment shownin FIG. 3, further be connected with respective control devices 20 viawhich--by means of a separate switch 21--different modes of operation ofthe hydraulic pump 1 can be set. Neither is this configuration shown inFIG. 4.

The operation of the selection valve 30, and therewith the selection ofthe operating pressure line 15a, 15b or load controlling the power ormoment regulation in accordance with the invention, could likewise beeffected by means of the control device 20.

We claim:
 1. A regulation device for an adjustable hydraulic pump havinga hydraulic servo setting apparatus for providing for smooth steplesssetting of the pump delivery quantity, in which the delivery quantitysetting is determined in dependence upon the delivery pressure of thehydraulic pump in a delivery pressure line and a control pressure in acontrol line, and the setting apparatus has a spring biasing a pumpsetting member in a first direction of maximum delivery quantity, and atleast one piston urging the pump setting member in a second oppositedirection of delivery quantity reduction, wherein the piston is actedupon via a hydraulically actuated control valve with the deliverypressure, and the actuation of the control valve is effected by thecontrol pressure in the control line, wherein a moment valve isprovided, the closure force of which is determined by a metering springarrangement which is connected with the pump setting member and isbiased in dependence upon the delivery quantity setting, wherein themoment valve connects the control line with the discharge in dependenceupon the control pressure in the control line and the biasing of themetering spring arrangement,characterised in that, a settable chokedevice, for setting the control pressure acting upon the control valveand the moment valve, is arranged in the control line which branches offfrom the operating pressure line of the pump.
 2. Regulation deviceaccording to claim 1, wherein the settable choke device comprises anelectrical quantity-proportional valve.
 3. Regulation device accordingto claim 1, wherein the settable choke device comprises a switch valveand choke arranged in parallel.
 4. Regulation device according to claim3, wherein a choke is arranged in the control line between the settablechoke device and the branch to the control valve and to the momentvalve.
 5. Regulation device according to claim 1, wherein a deliveryflow choke is arranged in the delivery pressure line, and the controlpressure and the delivery pressure are taken off on respectivelydownstream and upstream sides of the delivery flow choke.
 6. Regulationdevice according to claim 1, wherein the settable choke device isconnected with a control device, by which different modes of operationof the hydraulic pump are selected by a separate switch.
 7. A regulationdevice for an adjustable hydraulic pump having a hydraulic servo settingapparatus for providing for smooth stepless setting of the pump deliveryquantity, in which the delivery quantity setting is determined independence upon the delivery pressure of the hydraulic pump in adelivery pressure line and a control pressure in a control line, and thesetting apparatus has a spring biasing a pump member in a firstdirection of maximum delivery quantity, and at least one piston urgingthe pump setting member in a second opposite direction of deliveryquantity reduction, wherein the piston is acted upon via a hydraulicallyactuated control valve via a hydraulically actuated control valve withthe delivery pressure, and the actuation of the control valve iseffected by the control pressure in the control line, wherein a momentvalve is provided, the closure force of which is determined by ametering spring arrangement which is connected with the pump settingmember and is biased in dependence upon the delivery quantity setting,wherein the moment valve connects the control line with the discharge independence upon the control pressure in the control line and the biasingof the metering spring arrangement,characterised in that, the deliverypressure line branches into at least two operating pressure lines, fromeach of which a separate control line branches off, and in each of whichcontrol lines a choke device is provided, and wherein the control linesare selectively connectable with the control line by a selection valve.8. Regulation device according to claim 7, wherein each settable chokedevice comprises an electrical quantity-proportional valve. 9.Regulation device according to claim 7, wherein each settable chokedevice comprises a switch valve and choke arranged in parallel. 10.Regulation device according to claim 9, wherein a choke is arranged inthe control line between the selection valve and the branch to thecontrol valve and to the moment valve.
 11. Regulation device accordingto claim 7, wherein a delivery flow choke is arranged in the deliverypressure line, and the control pressure and the delivery pressure aretaken off on respectively downstream and upstream sides of the deliveryflow choke.
 12. Regulation device according to claim 7, wherein eachsettable choke device is connected with a control device, by whichdifferent modes of operation of the hydraulic pump are selected by aseparate switch.